Fluid cooled electromagnetic structure for traveling wave tubes



INVENTORS 6749/7, fiw/ My ref flev'e/"fa/waz/ ATTYS.

I, T X Q y, fl I! I i F; 7 ///A H. GLIEN ETAL Filed NOV. 20, .1968

FOR TRAVELING WAVE TUBES FLUID COOLED ELECTROMAGNETIC STRUCTURE Nov. 3,1970 2 a M l R H N m QN I l. I 1 6| L 1// l m 1 H M 7/ m 7 PM a w? 1 Twm mwwmmezs Q 5;;

United States Patent Oifice 3,538,366 Patented Nov. 3, 1970 US. Cl.313-24 6 Claims ABSTRACT OF THE DISCLOSURE An arrangement for thebundled guidance of an electron beam in a traveling wave tube having atleast one fluid cooled magnetic coil, in which the latter is dividedinto a plurality of individual coil sections disposed on a tubularlyshaped double-Walled carrier body, on Which are also disposed coolingfins which are interposed between respective pairs of adjacent coilsections, with inlet and outlet connections being provided for effectingthe passage of coolant between the double-wall of the carrier body.

BACKGROUND OF THE INVENTION The invention relates to an arrangement forthe bundled guidance ofthe electron beam of a traveling wave tubeutilizing at least one fluid cooled electromagnetic coil and radiallyextending heat conducting plates or the like.

Magnet arrangements of this general type are known in the prior art (seefor example The Bell System Technical Journal, 42 July 1963, No. 4, part3, page 1832). However, the magnetic field values attainable withpermanent magnet systems are no longer suflicient for the bundling ofelectron beams of high perveance, and in their place electromagneticcoil arrangements must be utilized, which because of their relativelyhigh power loss of several kw. are generally cooled by means of asuitable liquid. As a consequence, various proposals have heretoforebeen made for the design of such type of fluidcooled electromagneticcoils. Thus, for example, in one embodiment, proposed in the above citedarticle, water conducting cooling coils are disposed adjacent the radialsides or ends of the control coil. However, in many cases such coolingis inadequate and ultimately leads to a considerable localization ofheat within the coil.

It has been attempted to eliminate these difficulties by forming theelectromagnetic arrangement into a plurality of individual coils whichwere separated by water cooled plates (see Journal of Electronics andControl, 1. Ser. vol. 14, No. 1, January 1966, page 41).

However, in this type of magnetic arrangement, the division of the coilstructure into individual coil sections cannot be carried sufficientlyfar to solve the cooling problems of the individual coil sectionsarranged between the water cooled plates, because the necessarythickness of the latter to provide adequate stability producesdetrimental effects with respect to the magnetic field produced by thecoil structure. Furthermore, this type of construction results in anenlargement of the outer diameter of the coil structure without acorresponding magnetic gain, due to the disposition of the cooling fluidfeed connections at the outer circumference, which in turn, in mostcases, further complicates the installation of traveling wave tubes withsuch focusing coils into the load circuit. The technical coolingproblems concerning electromagnetic coil focusing arrangements know inthe prior art can be brought within reasonable limits by designing thecoils with very large dimensions, i.e. having a relatively large outerdiameter for a predetermined inner diameter of a size to receive thetraveling wave tube, as in such case the power loss to be dissipated issmaller than in a comparable coil with a smaller outer diameter.However, this results in the handling of the coils and retaining framestherefor of suflicient stability being more cumbersome because of theadditional relatively great Weight involved.

.BRIEF SUMMARY OF THE INVENTION The invention is directed to the problemof avoiding the disadvantages of the magnetic arrangements known in theprior art and to produce an arrangement which, even with increased powerlosses resulting from a reduction in the outer diameter of the coil,still assures adequate cooling of all portions of the coil.

In the proposed solution, according to the invention, of this problem,the electromagnetic arrangement comprises a fluid cooled magnetic coildivided into a plurality of individual coil sections which are placed ona common tubular carrier body of double-walled construction, which isprovided with inlet and outlet connections for the cooling fluid, onwhich carrier body radially extending cooling ribs or fins are disposed.The respective cooling fins may be of annular disc-like formation,extending perpendicularly to the longitudinal axis of the carrier bodyand respectively disposed between the individual coil sections of theelectromagnetic coil. The interior of the double wall of the carrierbody may be provided with partitioning means, preferably in the form ofa double pitch helix, whereby the inlet and outlet connections for thecooling fluid, for example water, are disposed at the same end of theelectromagnetic coil.

Such inlet and outlet connections for the cooling fluid of theelectromagnetic arrangement are preferably disposed at the end thereofadjacent the catcher of an inserted tube, enabling the use of anadditional, externally disposed coil at the opposite end of thearrangement, which coil may be specially designed to provided desiredfield strength characteristics adjacent the beam entrance into the areaof uniform field strength within the electromagnetic arrangement,thereby increasing the stability of the electron beam between theelectron gun and the adjacent end of the magnetic arrangement.

Eflicient removal of heat by means of the fluid cooled carrier bodymakes further possible the use of a plurality of relatively thin coolingfins or ribs which are sufficiently thin that they do not disturb thecourse of the magnetic field, and as a result thereof coil sections ofnarrow axial width may be employed, which when disposed between twoconsecutive fins substantially completely eliminates the existence ofany localization of heat within the coil sections. Furthermore, byemploying individual coil sections with different winding arrangements,a desired predetermined course of the magnetic field can be achieved.

Furthermore, by utilization of an arrangement in which the fluid coolingis disposed within the coils, enabling the simultaneous use of thecooling structure as a carrier body for the respective windings,exceptionally good thermal contact can be provided between the carrierbody and the cooling fins for example by means of a soldered connection,which type of structure is practically unattainable where an externallyarranged cooling structure of tubular shape is employed which, forexample, must be pushed or suitably shrunk on, over the cooling fins ofthe completed coil assembly.

Any possible localized residual heat still remaining, primarily betweenthe insulated layers of the wire, can be eliminated by effecting thewinding operation by means of a so-called wet winding operation withepoxy resin and a subsequent hardening thereof, to provide a moreefficient heat conduction through the coil structure and at the sametime improving the mechanical strength of the coil.

BRIEF DESCRIPTION OF THE DRAWING The figure of the drawing represents alongitudinal sectional view through an electromagnetic structure,constructed in accordance with the present invention, for a travelingwave tube.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the embodiment of theinvention illustrated, the electromagnetic coil is divided into aplurality of individual, annular shaped coil sections 1 to 14 which aresupported on an elongated tubular shaped carrier body of double-walledconstruction, comprising a pair of concentric tubular walls 31, thespace therebetween being closed at the respective ends of the bodystructure, with the latter thus extending through the central opening ineach of the coil sections. Secured, in good heat conducting relation, tothe exterior wall 31 of the carrier body are a plurality of cooling ribsor fins, made for example of brass and soldered to the adjacent wall 31,with the respective cooling fins being disposed between adjacent coilsections. A suitable hollow conductor 18 is connected at the catcher endof the structure by means of which the high frequency energy of the tubemay be conducted therefrom, and disposed at the ends of theelectromagnetic arrangement are respective pole plates 16 and 17 of ironor the like, whereby the magnetic field produced at the ends exhibits ahigh flank steepness with almost a vertical rise to the saturationvalue. Disposed adjacent the pole plate 17 and separated therefrom by aspacer ring 19, for example of brass, is an external coil which producesa magnetic field adjacent the entrance into the electromagneticarrangement whereby the electron beam initially enters a fieldexhibiting a small maximum following which a minimum is traversed priorto entry into the uniform field, which construction promotes aparticularly efiicient guidance of the electron beam entering from theleft, as viewed in the figure, along the axis 34 of the followingmagnetic arrangement, only a portion of the adjacent structure at theentrance end of the electromagnetic arrangement being illustrative.

In addition, a tubular metal cylinder, not shown, can be inserted in thecarrier body, such cylinder or tube being provided at its opposite endadjacent the catcher with an edge of irregular shape, such that itcompensates for irregularities in the field of the coil.

The coil section 1 adjacent the catcher end of the electromagneticarrangement is provided with a larger internal diameter than theremaining coil sections to provide space for the accommodation of inletand outlet connections 22, 23, disposed one behind the other as viewedin the figure, the inner ends of which connections communicate with theinterior between the walls 31 of the carrier body whereby fluid cancirculate therebetween. To effect a distribution of cooling fluid overthe entire area of the carrier body suitable partition means is disposedbetween the respective walls 31 of the carrier body, such partitionwalls being arranged to provide a circuitous fluid flow between theinlet and outlet connections. In the embodiment illustrated suchpartition means is in the form of a double pitched helix, formed by wire33 of suitable gauge, disposed in fixed relation between the wall 31with the pitch being so selected that the cross-sectional area of therespective passageways formed thereby is equal to the cross-sectionalarea of the respective inlet and outlet connections. If it is desired toincrease the travel, this may be readily accomplished by utilizing asuitable multiple pitch greater than 2.

Good heat conduction between the respective coil sections and thecarrier body and cooling fins carried thereby may be achieved byembedding the respective coil sections in epoxy resins, of the typecommonly employed in connection with potted structures, wherebyexceptionally good heat-conducting contact will be effected betweenadjacent surfaces of the respective coil sections and cooperable coolingfins and external wall 31 of the carrier body. Preferably the winding ofthe respective coils is effected by means of a so-called wet windingoperation employing an epoxy resin paste which is subsequently permittedto harden, whereby the resulting coil section is in the form of a solidblock, having increased mechanical strength and providing efiicient heatconduction from the coil interior outwardly to eliminate any possibleremaining residual heat concentration within the coil section whichprimarily occur between the insulated layers of the wire forming thecoil.

Having thus described our invention it will be apparent that variousimmaterial modifications may be made in the same without departing fromthe spirit of our invention, hence we do not wish to be understood aslimiting ourselves to the exact form, construction, arrangement andcombination of parts herein shown or described.

What we claim is:

1. An arrangement for the bundled guidance of an electron beam intraveling wave tubes having at least one fiuid cooled magnetic coilprovided with cooperable heat dissipating members thereof, characterisedby the fact that each fluid cooled magnetic coil is divided into aplurality of individual annular shaped coil sections, a tubular shapeddouble-walled carrier body on which said coil sections are disposed,radially extending cooling fins disposed on said carrier body andconnected thereto in good heat conducting relation therewith, saidcooling fins each being disposed between a respective pair of adjacentcoil sections, in good heat conducting relation therewith, and fluidinlet and outlet connections secured to said carrier body foroperatively supplying a fluid coolant to the interior of said carrierbody.

'2. An arrangement according to claim 1, comprising in furthercombination, partition means disposed in said carrier body between thedouble-wall thereof, for distributing fluid flow across substantiallythe entire effective cooling area of said body.

3. An arrangement according to claim 2, wherein said partition means isof helix configuration and is at least of double-pitch.

4. An arrangement according to claim 1, wherein each coil section isembedded in epoxy resin.

5. An arrangement according to claim 1, wherein said inlet and outletconnections are disposed at the end of the carrier body which is to beadjacent the catcher end of a cooperable traveling wave tube when thelatter is disposed in operating position in said body.

6. An arrangement according to claim 5, wherein each winding turn of acoil section is embedded in epoxy resin to provide improved heatconduction from the interior of such coil section outwardly.

No references cited.

JAMES W. LAWRENCE, Primary Examiner C. R. CAMPBELL, Assistant ExaminerUS. Cl. X.R.

